Logic signals in optical form have been combined in a single semiconductor structure wherein each logic variable is a different wavelength. The structure in which the logic combination takes place involves several semiconductor materials each having a different band gap for each different frequency. Such a structure is illustrated in Electronics, Sept. 8, 1981, page 42. In this complex heterostructure, diffusion is the carrier transport mechanism so that there will be a limit on speed of responsiveness.
In a copending application filed concurrently herewith, identified as Ser. No. 454,784, by the inventors Chappell, Jackson and Woodall, an optical conversion structural principle is set forth wherein in a semiconductor material with an undoped layer with a thickness of the order for ballistic transport bounded by a tunneling barrier that is of the order of the mean free path of a carrier in the tunneling portion of the semiconductor material, drift becomes the carrier transport mechanism and a much higher output voltage and higher speed of response is achieved.